This invention relates to a structural arrangement for a track frame and associated parts for crawler or track-type vehicles and to a structural arrangement of the track frame with the supporting frame for the vehicle.
In crawler or track-type vehicles particularly those which require erection in the field, such as power shovels, in order to facilitate shipment crawler side frames including the drive sprocket for the track, idler roller and supporting track rollers are conventionally manufactured as completely separate items which are subsequently to be bolted or otherwise attached to a supporting frame or undercarriage for the vehicle. In considering the load transmission characteristics of such a structure it can be seen that this creates a chain of connected structures, and each link in the chain of connected structures is required to withstand the entire design load. For example, the track rollers supporting a crawler track receive loads through the side frames carrying the track, from the lower frame or undercarriage of the vehicle. Each of the structures and connections must be designed to handle the maximum load conditions. Accordingly, this form of construction for track-type vehicles is unduly complex and expensive by reason of the number of separate portions of the structure which must be designed and constructed to carry the entire design load.
With regard to those types of crawler or track-type vehicles which must be assembled in the field it is conventional to manufacture and ship the entire crawler frame structure including the sprockets and idle rollers which must carry the track as an integral unit which is subsequently attached to the supporting frame or undercarriage of the vehicle. Particularly with regard to the larger vehicles of this type, i.e., power shovels, these crawler frames are exceedingly long and heavy for shipping purposes and thereby difficult and expensive to handle. It has been suggested in the prior art that the foregoing problem can be solved by making the drive portion of the crawler frame, i.e., the crawler sprocket and associated gearing and drive motor a separate modular portion of the crawler frame. However, in so doing, unsatisfactory provision is made for providing track rollers which will prevent those lower portions of the track adjacent the crawler sprocket from buckling, or stated another way, insufficient provision is made for load equalization along the entire length of the lower portion of the track between the crawler sprocket and the front idler roller.
It is, therefore, an object of the invention to provide a crawler or track frame structure in which satisfactory provision is made for load equalization along the entire length of the lower portion of the crawler track from idler roller to crawler sprocket.
It is another object of this invention to provide for a track-type vehicle a main frame and crawler frame structure which for load transmission purposes is an integral structure.
A further object of this invention is to provide in a modularized crawler frame structure an arrangement for a track roller or rollers adjacent the idler roller and crawler sprockets which provides for greater load equalization and which can respond to changes in level of the track as it proceeds from the idler roller or to the crawler sprocket.